Stochastic Comparisons of Two-Units Repairable Systems

We consider two models of two-units repairable systems: cold standby system and warm standby system. We suppose that the lifetimes and repair times of the units are all independent exponentially distributed random variables. Using stochastic orders we compare the lifetimes of systems under different assumptions on the parameters of exponential distributions. We also consider a cold standby system where the lifetimes and repair times of its units are not necessarily exponentially distributed

Some New Results on Nonconformable Fractional Calculus

In this paper, we present some results for a local fractional derivative, not con-formable, defined by the authors in a previous work, and which are closely relatedto some of the classic calculus.Fil: Nápolos Valdés, Juan E.. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Matemática; ArgentinaFil: Guzmán, Paulo Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Matemática; ArgentinaFil: Lugo, Luciano M.. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Matemática; Argentin

A Framework for Printing and Minting Plans

This paper presents alternative models for forecasting the demand for bills and coins of different denominations. When compared to the models often used, the root mean squared forecasting error is substantially reduced. The paper also develops a new framework to formulate the printing and minting programs by using density forecasts along with information on technological constraints and preferences of the policy maker.

Herbivory on the pedunculate oak along an urbanization gradient in Europe: Effects of impervious surface, local tree cover, and insect feeding guild

Research ArticleUrbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that—just like in non-urban areas—plant– herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactionsinfo:eu-repo/semantics/publishedVersio

Autocalibration with the Minimum Number of Cameras with Known Pixel Shape

In 3D reconstruction, the recovery of the calibration parameters of the cameras is paramount since it provides metric information about the observed scene, e.g., measures of angles and ratios of distances. Autocalibration enables the estimation of the camera parameters without using a calibration device, but by enforcing simple constraints on the camera parameters. In the absence of information about the internal camera parameters such as the focal length and the principal point, the knowledge of the camera pixel shape is usually the only available constraint. Given a projective reconstruction of a rigid scene, we address the problem of the autocalibration of a minimal set of cameras with known pixel shape and otherwise arbitrarily varying intrinsic and extrinsic parameters. We propose an algorithm that only requires 5 cameras (the theoretical minimum), thus halving the number of cameras required by previous algorithms based on the same constraint. To this purpose, we introduce as our basic geometric tool the six-line conic variety (SLCV), consisting in the set of planes intersecting six given lines of 3D space in points of a conic. We show that the set of solutions of the Euclidean upgrading problem for three cameras with known pixel shape can be parameterized in a computationally efficient way. This parameterization is then used to solve autocalibration from five or more cameras, reducing the three-dimensional search space to a two-dimensional one. We provide experiments with real images showing the good performance of the technique.Comment: 19 pages, 14 figures, 7 tables, J. Math. Imaging Vi

The Absolute Line Quadric and Camera Autocalibration

We introduce a geometrical object providing the same information as the absolute conic: the absolute line quadric (ALQ). After the introduction of the necessary exterior algebra and Grassmannian geometry tools, we analyze the Grassmannian of lines of P^3 from both the projective and Euclidean points of view. The exterior algebra setting allows then to introduce the ALQ as a quadric arising very naturally from the dual absolute quadric. We fully characterize the ALQ and provide clean relationships to solve the inverse problem, i.e., recovering the Euclidean structure of space from the ALQ. Finally we show how the ALQ turns out to be particularly suitable to address the Euclidean autocalibration of a set of cameras with square pixels and otherwise varying intrinsic parameters, providing new linear and non-linear algorithms for this problem. We also provide experimental results showing the good performance of the techniques

Effect of forcing vine regrowth on 'Tempranillo' (Vitis vinifera L.) berry development and quality in Extremadura

In warmer regions, fruit ripening in the wine grape tends to take place during the hottest part of the growing season. This can have negative consequences on the qualitative characteristics of the grape berries at harvest. Forcing vines to regrow can be an aggressive but effective technique to delay the harvest date, but needs to be evaluated carefully in each growing condition. In 2017, in an experimental vineyard in Extremadura, forcing was conducted 3 (F1 treatment) and 22 (F2 treatment) days after anthesis (May 18 and June 6) by hedging growing shoots to seven nodes and removing summer laterals, leaves and primary clusters. Vines grown using conventional practices were used for the Control treatment. Forcing delayed the harvest date from August 22 (Control) to September 14 (F1) and October 19 (F2). Shifting the berry growth period modified the duration of the different fruit development stages. Compared to the Control treatment, the F1 and F2 berries were smaller at harvest, but had similar skin weight percentages; however, the seed weight percentage of the F2 berries was higher. The differences in grape composition observed at harvest between the various treatments were further accentuated in the wines. At harvest, the F2 berries had significantly higher total polyphenol and anthocyanin content than the Control and F1 berries, which had similar values. In the wines, both F1 and F2 characteristics differed considerably from the Control, most notably in the high F2 tannin concentration. These preliminary results from the first year of study indicate the potential of this technique to obtain wine grapes with very different characteristics, offering new viticultural perspectives in warm climate areas